The circulation of hot or chilled water to provide heat or cool spaces is known as a hydronic system. A hydronic system is composed of many subsystems such as, for example, boilers, chimney, vertical supply and return piping, horizontal supply and return piping, pump, and convectors, and so forth. Such hydronic heating and cooling systems are based on distributed hydronic networks. In a complex hydronic system such as, for example, a building heating system, hot water is pumped from a central boiler up a common riser from which it flows through a multiplicity of branch lines each including one or more terminals. Then, the multiple streams are reunited in a common downpipe that leads back to the boiler. In such a system it is necessary to balance the flow in the individual branches to achieve the desired technical and economic performance of the system. Thus, each branch can be provided with a balancing valve, which can be provided in the form of a lockable flow-control valve that can be adjusted until a predetermined flow, normally measured in gallons per minute, is obtained in the branch.
A hydronic network represents a complex system that requires the ability to simultaneously correctly solve design, sizing and control-related issues. A design error in one part of the hydronic network affects the rest of the network. Moreover, to correct poor operations associated with unbalanced networks, (e.g., hydronic networks without balancing) building operators typically increase the head of pumps and/or hot water supply temperatures to ensure comfort in all zones of the building. Such an approach results in increased energy consumption with respect to the pumps and probable growth of primary energy to produce hot water, overheating of hydraulically favored zones, and in some cases instability of control loops. Such manual balancing is time consuming and requires a number of iterations.
The majorities of prior art methods for balancing distributed hydronic networks are based on iterative approaches and are decentralized in nature. Such a decentralized approach may control each balancing valve independently via the use of a local control algorithm without any communication between individual balancing valves. Consequently, special equipment must be installed on each of the balancing valves, which decreases the economic performance of the overall system. Additionally, such prior art methods require a number of iterations for the calculation of settings of balancing valves, which is a time-consuming process.
Based on the foregoing it is believed that a need exists for an improved method and system for model-based multivariable balancing with respect to distributed hydronic networks as described in greater detail herein.